Varnish is a web application accelerator, which has been gaining a lot of popularity in recent years, because it can increase the load speed of any site, sometimes even by 100%, depending on the content. This tool is occasionally referred to as a caching HTTP reverse proxy too and is used to lower the overall server load and to accelerate the browsing speed for the site visitors. Every time a visitor opens a page on a particular website, the web browser request is processed by the web server and the requested content is sent as a response. If the Varnish accelerator is enabled, it caches the pages that the website visitor browses and in case any of them is accessed once again, it’s fetched by Varnish and not by the server directly. The boost in the performance is due to the fact that the accelerator processes the web requests significantly quicker than any web server, which results in much faster browsing speeds for the users. If any content is edited in the meantime, the cached pages will also be ‘refreshed’ the next time somebody attempts to access them.